1. Field of the Invention
This invention relates to test equipment for integrated circuits and semiconductor devices. It relates particularly to an apparatus for semiconductor device testers for marking computer chips with ink.
2. Description of the Prior Art
Semiconductor device testers and more particularly, the Trillium.TM. tester model micro-master II (FIG. 1) 10 (Trillium is a trademark of LTX corporation, 3970 North First street, San Jose, Calif.) is used to electrically test semiconductor chips on a wafer to determine individual chip performance and yields.
When a chip fails an electrical test, the tester 10 places a round ink spot on the chip so the chip can be rejected in later processing, such as in wafer slice and chip picking operations. In subsequent processing steps, computer chips having an ink spot will be separated from the good chips.
A major shortcoming of the current electrical testers and more particularly Trillium.TM. testers Model micro-master-II is that excessive effort and time is required to change the device that puts the ink on the chips (inker). The prior art mounting of the ink dispenser makes changing and aligning the ink dispenser difficult and time consuming. Also, its location makes it difficult to work on and make adjustments.
The tester comprises a test head and a prober station. In operation the prober station moves into position under the test head. A wafer is positioned on a chuck that moves from an unload/load position to a test position under the prober opening in the stage.
An ink dispenser is mounted on a stage overhanging the wafer/chuck in the test position. The ink dispenser is device which marks ink on to an underlying computer chip. In operation the chuck moves the computer chips into test positions and chip marking position. The ink dispenser is cable connected to a pen box controller that sends electrical signals to a pen driver mechanism that moves a pen into contact with a chip thus marking the chip with ink. Moreover, the alignment of the ink dispenser to the chuck is critical to ensure that the correct chip is properly marked in the center of the chip.
During the repeated testing and marking of computer chips, the ink dispenser can vibrate out of alignment causing the ink spots produced to be misaligned or imperfect in shape. Also, periodically the ink dispenser runs out of ink and must be replaced. However, with the current arrangement, replacing and aligning the ink dispenser is very labor intensive and requires over one half hour to reset/realign the ink dispenser in the correct position in relationship to the chip.